Animal Waste, Water Quality and Human Health

388Animal Waste, Water Quality and Human HealthQuestion 15: Type of Exposure. There are various ways in which people can beexposed to pathogens in contaminated recreational waters. We extend the scopehere slightly to include occupational exposures as well, for example peopleharvesting food from such waters or washing clothes, or involved in religious orother custom. Exposure to contaminated irrigation waters, for example, fromapplying water or exposure to spray from overhead irrigations, is alsoconsidered. The options presented and relative risk weightings are:Swimming relative risk = 1Other primary (wading, working, etc.) relative risk = 0.3Secondary (splashing, wet equipment) relative risk = 0.1Irrigation relative risk = 0.1Question 16: Is Time of Exposure Likely Correlated with Contamination Events.As discussed earlier, there may be situations in which contamination events andexposure are correlated. Where correlations may significantly alter risk, thefollowing relative risk factors are applied:Correlation unlikely relative risk = 1Possible increased likelihood relative risk = 10Possible decreased likelihood relative risk = 0.1Probable increased likelihood relative risk = 100Probable decreased likelihood relative risk = 0.01These factors are only included in the risk calculations where both the exposurefrequency is “weekly” or less and the contamination frequency is “intermittent”or less. An additional question is included to enable users to model the effect ofscenarios and factors not easily assessed via the other questions in the model.For this question, the user enters a value to represent how much better, or worse,the risk to human health from exposure to that recreational water would be withthe additional factor considered. Thus, if the situation, due to some other factoris ten times worse, then the user should enter “10” in the space provided andselect “increase by this factor” in the list provided. If the situation is only half asbad due to some intervention or other factor not specifically included in themodel, the user would enter “2” in the space provided and select “decrease bythis factor” in the list provided. If there is no effect the user can enter “1”, or“0”, or leave the box empty.10.4.4.4 Relative risk calculationsThe answers to the above questions are translated into the relative risk valuesshown above. These values are then used in calculations to establish how therelative risk from each factor affects the relative risk overall. In general the